DNA and RNA
DNA is an abbreviation for Deoxyribonucleic Acid. This material is what is responsible for transferring genetic information in cells that accounts for the different traits that organisms can take on. Several scientists have worked to do research on the subject and several did the first work to start out the field.
Griffith did experiments with the first vaccinations and was trying to find a way to create a vaccine. He worked with two types of bacteria of the same species: Smooth and rough. He followed the following steps while experimenting:
Because of these findings, Griffith concluded that something passed from the dead smooth bacteria into the live rough bacteria that made them deadly to the mice. He called this phenomenon "transformation."
Avery was responsible for determining that it was the DNA and not the protein that determines the traits of organisms and transmits genetic information.
Hershey and Chase
Hershey and Chase were a pair of scientists that tried to study genetics through the use of bacteriophages. Bacteriophages are viruses that infect bacteria. They used radioactive DNA to trace its progress from the viruses to the bacteria. They found that when they made the protein radioactive, it was not passed on but when they made the DNA radioactive, it was passed on. Because of this, they were able to conclude that the DNA was the material that was passed on and not the protein.
Owen Chargaff was the scientist who discovered the rules that determine what bases bond to each other. Thus, when explaining these things, the term "Chargaff's Rules" can be used.
DNA is made up or three parts: a sugar backbone, phosphates, and Nitrogenous bases. There are two types of bases: pyrimidines and purines. The purines have two rings of atoms while pyrimidines have only one ring. Pyrimidines consist of Thymine and Cytosine and the Purines consist of Adenine and Guanine. Also, another base called Uracil is also a pyrimidine and is only used in RNA molecules as a replacement for Thymine which is not used in RNA. In a DNA molecule, Cytosine can only bond to Guanine and Adenine and only bond to Thymine. Hint: The pyrimidines have Ys in their names except for Uracil, which is also a pyrimidine.
Structure of DNA
DNA forms a structure called a double helix. It is formed by two spirals winding around each other. They are connected by the bases which are bound by either two or three hydrogen bonds. (Adenine and Thymine have two, Guanine and Cytosine have three). The spiral is composed of alternating sugars and phosphates. The sugar is deoxyribose which yields the name Deoxyribonucleic Acid which is abbreviated as DNA. The bases are connected to the sugars by covalent bonds and the phosphates and sugars are also connected by covalent bonds. There are eleven nucleotide sequences per full turn of the helix.
RNA is a chemical substance similar to DNA that functions to help produce proteins in cells. Several similarities and differences exist between RNA and DNA as shown blow:
|Uses Deoxyribose as the sugar for the backbone.||Uses Ribose as the sugar for the backbone.|
|Has two strands of genetic material||Has one or no strands of genetic material. mRNA has one strand while tRNA and rRNA have different forms that don not consist of strands.|
|Uses the bases A, T, C, and G.||Uses the bases A, U, C, and G.|
Types of RNA
There are three types of RNA: